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Patented Jul l9, I898. 607,426' w. M. DUCAT. y

PURIFYING SEWAGE, 81.0., BY BACTERIAL ACTION.

(Application filed Oct. 5, 1897.)

2 Sheets-Sheet I (No Model.)

@m Wov Ka Wow ago.

me Nonms PETERS cn.. FHOTD-LITHO., WASHINGTON. n. c.

(Nu Model.)

- Patented luly 19, 1398. w. m. DUCAT.

PURIFYING SEWAGE, &c., BY BACTERIAL ACTION.

(Application filed Oct. 5, 1897.)

@mmYO u UNITED STATES ATENT OFFIC WALTER ill/\RDON DUCAT, OF LONDON, ENGLAND.

PURIFYING SEWAGE. 8 410., BY BACTERIAL ACTION.

SPECIFICATION forming part of Letters Patent No. 607,426, dated July 19, 1898.

Application filed October 1897. Serial No. 654,110. (No model.) Patented in Trance May 18, 1897, No. 267,048, aud in Belgium May 19, 1897, No. 128,347.

To all whom it may concern:

Be itknown that I, XVALTER MARDON DUCAT, colonel late Royal Engineers, of 1-3 ll)evonshire Terrace, Hyde Park, LondonJVi, England, have invented new and useful Improvements in and Connected with the Puri fication of Sewage-or other Foul Liquids by Bacterial Action, (for which I have obtained Letters Patent in the following countries, viz: Belgium, dated May 19, 1897, No. 128,347, and France, dated May 18, 1897, No. 267,048,) of which the following is' a full, clear, and

exact description.

diminished by exposure to cold winds or the.

process of purification being interrupted by frost, which would cause the cessation of bacterial action.

lleretofore filter-beds have usually been submerged or covered with the liquid to be purified, so that while the filter was in operation access of air to and into the filter-bed was not possible, such access of ail-being only possible during the periods of rest when the system of intermittent filtration was adopted, and as the surface only of the filter-bed was exposed to the air long periods of rest were required, during which periods .the filter was of course standing idle. The superficial aeration thus obtainable was insufficient to maintain the bacteriological efficiency on which the purifying action is found to depend, it having been discovered that for the purification of sewage and other foul liquids a high degree of aeration is necessary to supply the oxygen required, the filter-bed having for its principal function to act not as a mechanical strainer, but as the nidus for the microbes by which the organic impurities are destroyed.

According to my invention the continuous aeration of the filter-bed throughout its whole mass is insured by natural means and in such a manner that the aeration is directly brought about by the working of the filter itself, so that the aeration, beingentirely independent of adventitious aid, is rendered continuous, and the efficiency of the purifying action is so complete that the working of the filter may be continued for an indefinite period without intermission, the whole of the solid matters.

suspended in the sewage being disposed of by bacterial action, so that no renewal or cleaning is required. This result is attained by providing for the continuous penetration .of'the ambient air into the midst of the mass filter-bed that the latter shall never be fully charged with liquid, and consequently shall never be submerged. The maintenance of the bacterial action during cold weather is provided for by inclosing the filter in an outer air-chamber, so as to screen it from cold winds,-

and by supplying to this chamber from which the air for aerating the mass is drawn air which has been previously warmed either by the internal action of the filter itself or by an external source of heat.

The invention will be described with reference to the accompanying drawings, forming part of this specification, wherein- Figure 1 is a half-plan and half-horizontal section of a filter, the section being taken'on.

two different planes. Fig. 2 is'a vertical section of the filter. Fig. 3 is a part elevation of one of the apertured Walls. Fig. 4 is an enlarged sectional detail view of one of the sewage-supply troughs. Fig. 5 is a part vertical section showing a modified construction of the means of aerating the beds by lateral admission of air.

The walls A of the filter are apertured orwork.

constructed of open-work, such as honeycombed brickwork, or, preferably, of superposed rows of earthenware pipesa, laid in cement, the walls thus openly constructed throughout their whole length and height being erected between pillars of solid brick The pipes a extend, preferably, in. a downwardly-inclined direction from the outside to the inside of the wall, so as, while con-V the adjacent strata azof finer material,- and in these verycoarse strata there, may be laid pipes a, forming open-jointed continuation's of'certain of the air-inlet pipes a, At the bottom of the filter is a drainage layer of large pebbles, in which are laid open-jointed pipes B, leading to outlets b in the walls A, discharging into a gutter b, by which the ciliaent is carried away. 4 r p In order to produce the exhaustive action by which the air is caused to be drawn into the mass of the filter, the liquid to bepurified is supplied to the filter-bed in as uniformlydistributed a form as possible and at such a" rate compared with the rate of flow through the mass that the surface of. the bed is never submerged, andthe mass is never saturated to such an extent that there is any head of liquid-pressure in the chamber nor any tend ency of the liquid to run out until it reaches 'the dischargeapertures b at the bottom of the chamber. The distribution of the sewage-to; the filter may be effected by allowing it to overflow the sides of troughs D, extending across the filter-bed and supplied through spouts e from amain trough E, the troughs D"being provided with means of adjustment d at one end, whereby they be brought so nearly horizontal that the overflow from the troughs D will be as nearly'ias' possible uniform over their whole length.

By supplying the liquid to thefil'ter in lim ited quantity it'b'ecomes possible to so distribute the liquid in the filter-beds that the,

coarsest stratum F to the lowermos'tand finest stratum F The uppermost stratum F is composed, preferably, of coke or cindcrs or other material-such as pumice-stone, burnt ballast, or gravel, for instance-say of about one cubic inch in size and about two'feet thick. The intermediate strata F F are resnectively of, say, half an inch and a quarter uniiorm andaboxte' 'say 409' Fahrenhoihthe morepipes h, passing horizontally through :the mass of the filter-bed, so that when the of an inch coke, and'the bottom stratum F is of, say, one-eighth of aninch coke. Although these dimensidns are indicated as suitable for purifying-sewage, I would have it understood that they are in -no way obligatory and may be varied according to circumstances, the thickness of the strata and the depth of the.

filter depending on the impurity of the sew a e. and the degree of purification required,

the essential feature being that the "uppermost stratum is the coarsest and is composed of pieces of such large dimensions as to leave interstitial spaces'sufiiciently large to enable the sludge or solid matters of the sewage to penetrate the mass of the u-pperstratum and v to be-there broken down and disposed of by 1 bacterial action without liability of the filter ever becoming choked withsolid matter. By

graduating the various strata progressively .from very coarse at the upper part to finer toward the lower part the "interstitial spaces (which are proportional 'to the degree of coarseness of the material) are in such rela- 9o tion to the amount of solid'matter suspended in the liquid passing through them as toinsure a degree of aeration at all parts of the filter adequate to maintain the bacterial action necessary to enable-the solid matters t09 5 be rapidly and effectually disposed of."

Instead of or inaddition tothe'walls of the filters chamber being aperture'd the. lateral".vv

aeration 'of the filter-bed might be provided. for uy interposing between the walls and the Fig; 5, of such Very coarse lumps of material what the air will have free passage between them from above, the liquid being distributed only'ov'er the surface of the filter-bed proper, and thatfat' such a limited rate that there is neverafnyhead of pressure within the filterbed. Air-tubes a'may'extend from this airinlet wall-through coarse intermediate strata, as before. As, however, the tubular or ape;

ertured construction of y the wallsbefore des'cribedis sufficie'nt for the purpose and as the interpositionof the coarse lining-wall A would uselessl-y extend the superficial dimensions of the structure, it would not be generally-adopted and is only indicated here as a possible modification. i

In order to protect the filter-bed from cold and maintain the temperatu re of the mass walls of the filter are surroundedby an airchamber'G, i-nclosed within solid walls 9 and a roof, large doors-g being provided; in the walls g for admission of air in warm weather, which .doors are closed when the external temperature fallsbelowa certain point. Adjoining one of the outer walls g is a chamber II, communicating with the external air and connected with the'air-chamber G by one or external temperature is not so low as to necessitate recourse to artificial heat-the air will be supplied to the ainchainber only through I00 filterlebed'a vertical stratum or lining-wall A,

IO tinued severe frosts, however, a stove in the midst, of the filter-bed supplying liquid to'the these pipes and will become warmed by the hat'generated within the mass of the filter.-

bed by-the action of the filter. The superfluous internal heat isrthus utilized to raise the temperature of the fresh air entering the air-chamber and passing thence through the apertured walls, A, whereby the temperature .of the whole'i'nass is maintained uniform and excessive 'cooling of the lateral portions by incoming cold air is prevented. In long-conchambenH-inust be used to raise the temperature .ofthe air before its admission to the airrchamber, so "that air at the proper temperature' will be supplied to the filter through its perforated side f As above mentioned, the scope of the in- I v'ention is notlimited to the treatment of sewn age, whichis only cited byway of example, the invention being equally applicable for the purification effriver and other water conta'minated with'organic impurities, theobject of'the treatmentbeing to render such water fit for drinking. I y

Having now particularly described and ascertained the nature of my said invention and in what manner the same is to beperformed, I declare thatwhat I claim-is 1. The herein-described methodof insuring the continuous aeration .of a filter used for purifying sewage and other -foul liquids by bacterial action, which consists iu admitting ambient air through the sides, and into thebed and causing the same to flow through the bed and so limiting the supply of liquid to the filter that the filter-bed will never be-fully charged with liquid and the motion of the liquid through the bed" and consumption of the oxygen of the air will produce an exhaustive action whereby the air will be con tinuously drawn into the mass through the sides of the mass as described.

2. The herein-described method of insuring the efiicien't' aeration of foul liquids while traversing" the mass of filter-beds used to purify the said foul liquids consisting insupplying the foul'liquid to the filter-beds in such quantity as to spread the said liquid outin a film on the surfaces of the individual bodies constituting the filter-bed and simultaneously supplying air to the sides .of the said filterbeds'whereby the flow of the liquid will cause a circulation of air around the said bodies constituting the said filter-bed, whereby the foul liquid may beefficiently acted upon by tlie;air while in a finely-divided condition. y 3. A filter for purifying sewage and other foul waters by bacterial action having one or more filter-beds confined by walls 'ofan openwork structure adapted to confine the filterbed while giving freecontinuous'lateral admission of air into the midst of the filter-bed,

substantially as and for theipurpose specified.

4. A filter for purifying sewage and other foul waters by bacterial action, having Walls adapted to give free continuous admission of airinto the midst of the filter-bed, in combination witha contained bed of filtering material divided into superposed-strata graduated of progressively-decreasing coarseness in the downward direction substantially as and for the purpose specified.

' 5. A filter for purifying sewage and other progressively-decreasing coarseness by inter- VBIllIlg strataof very 'coarse material having aerating-pipes laid therein forming continua tions of the lateral air-inlet passages as specified.

' 7. A filter for purifying sewage-and other foul waters by bacteriaLaction, having walls adapted to allow admission of air to the contained filter-bed, and surrounded by an outer inclosing air-chamber so as'to exclude cold air and enable the temperature of the air to be raised before being supplied to the filter. 8. The combination, with a filter for p.u-rifying sewage and 'other foul waters by baa-' teria'l action having walls adapted to allow admission of air to the contained filter b'ed,

and surrounded by an outer inclosing air chamber, of lair-admission pipes passing through the mass of the filter-bed and leading in to said air-chamber so that'the airbefore being admitted to saidcham-ber will be warmed by the superfluous internal'heat ofth'e filter as described.

WALTER MARDON nuoA'r. In presence of- Q E. S. BROWNE, J. CONWAY. 

